President Obama arrived in Boston with the first lady this morning to address the community in the wake of Monday's deadly marathon bombing, acknowledging the devastation that had befallen the victims and their families but assuring a church gathering that the city "will run again."

"We may be momentarily knocked off our feet, but we'll pick ourselves up," Obama told an audience at the Cathedral of the Holy Cross in Boston's South End during an interfaith service called "Healing Our City."

"We'll keep going; we will finish the race."

The cathedral was Obama's first stop, where he offered a message of hope.

"Your resolve is the greatest rebuke to whoever committed this heinous act," the president told a crowd of dignitaries and families of the victims. "If they sought to intimidate us, to terrorize us, to shake us from those values that ... make us who we are as Americans, well it should be pretty clear by now that they picked the wrong city to do it," at which point many attendees jumped to their feet.

The president recalled his and Michelle Obama's first time in Boston as students and assured the city that the marathon attack was personal for them.

The president and first lady were also expected to meet with victims and first responders later today.

At the beginning of the service, Boston Mayor Thomas Menino stood up out of his wheelchair to address those gathered at the church. Menino was in the hospital a few days ago for surgery on his leg after he broke it during a fall Friday.

Menino praised those who helped at the site of the bombing on Monday left three dead, more than 170 injured and a city in mourning, saying he had never loved Boston and its people more before.

"No challenge nothing can tear down the resilience from the heart of this city and its people," the five-term mayor said. "We have never loved it, this people more than we do today. We love the brave ones who felt the blast but still raced to the smoke. We love the fathers and the brothers who took shirts off their backs to stop the bleeding. The mothers and the sisters who cared for the injured. The neighbors and the business owners, the homeowners all across the city."

Massachusetts Gov. Deval Patrick described the bombing as an attack on the U.S. ideals of "equality, opportunity freedom and fair play."

"And just as we cannot permit darkness and hate to triumph over our spiritual faith, so we must not permit darkness and hate to triumph over our civic faith," the Democratic governor said. "That cannot happen and it will not."

The family of Krystle Campbell, a 29-year-old Massachusetts native killed in the blasts, sat among dignitaries in the church today. Audience members openly cried as the president described her loud and cheerful nature.

Obama also paid tribute to the two other victims killed in Monday's explosions: 8-year-old Martin Richard and Boston University graduate student Lingzi Lu of China.

By 10:30 a.m., big name Boston politicians and celebrities had already begun to fill the pews in anticipation of the president's speech. Those in attendance included Mitt Romney and eldest son Tagg, Rep. Joe Kennedy and his wife, actor Bradley Cooper, Theresa Heinz Kerry, Rep. Niki Tsongas, Rep. James McGovern, Massachusetts Attorney General Martha Coakley and journalist Mike Barnicle.

The Boston Children's Chorus, the cathedral's choir and American cellist Yo-yo Ma performed during the service.

The cathedral seats more than 2,000 people. It is the "mother church" of the Roman Catholic Archdiocese of Boston and has intricate stained glass windows. The church says it is New England's largest and earliest stained-glass collection.

Marathoners sporting blue and yellow Boston Athletics jackets were also among those packed into the church this morning.

The mood before the service was joyful with attendees chatting and laughing with those seated, but a somber mood fell over the audience minutes the service began and visitors became silent as the cathedral choir sang and the crowd waited for the service to begin.